Furnace construction



2 Sheets-Sheet l I NVNTOR.

ATTORNEY.

G. E. SEIL.

Nov. 21, 1939.

FURNACE CONSTRUCTION Filed Feb. l5, 1939 NOV. 21, 1939., G. E- SEiL2,1869y FURNACE CONSTRUCTI ON Filed Feb. l5, 1959 2 Sheets-Sheet 2ATTORNEY.

Patented Nov. 21, 1939 l lPATENT OFFICE FUaNAoE CONSTRUCTION Gilbert E.sen, cynwya, ra., assignor to E. J.

Lavino and Company, poration of Delaware Philadelphia, Pa., a cox"-Appucation February 15, 1939, serial No. 256,504`

. Claims.

This invention relates to refractory units orv bricks for furnaceconstruction and to the linings produced thereby, and has foran'important object thereof the relief of the pressures due to 5` thedifference in expansion between the hot Vends and the cold ends ofrefractory units in service,

which pressures result, when the bricks areinstalled in the usualmanner, in a continuous loss of refractory material during periods ofservice due to crushing and to pinching-off of the hot ends of the brickor other construction units. The invention is particularly applicable tocurved portions of furnace structures, such as arched roofs,l arches,etc., and to structures which are cylindrical in shape, such as rotarykiln linings. Furnace structure such as Valls, roofs, arches. and rotarykiln linings are usually built from standard refractory' shapes known asstraights or squares, arch brick, key brick, -wedge brick, furnaceblocks, etc. The number and shapes of the brick required for theconstruction of any Y portion of a furnace varies with the size andshape of the structure desired, and the methods of calculating the brickcount for Aa furnace structure are general knowledge to those Skilled inthe art. Merely by way of example we can consider the count for a rotarykiln, the shell of which is 6'-0" inside diameter, and which Iisl tohave a 9" lining. Reference to the published tables shows that arefractory ring 6'-0" outside diameter by 46 'inside diameter by 41/2"wide can be built from 91 standard` No. 1 wedge brick, which' are 9 x4%" and the edges of which are tapered from 21/2" to 1%". The number ofrings needed is determined by dividing the length of the kiln in inchesby 41/2". When tables are not available the number off'21/2" wedge brickneeded for the ring can be calculated by dividing the outsidecircumference df the circle (226.2" when the kiln is 6-0" in diameter)by 2/2" or 91. Then dividing the inside circumference of the circle(169.6 in thiscase) by 91 we obtain 1%" as the average thickness of theinside face of the wedge required. Since 2%" to 1%" is the taper on astandard No. 1 wedge brick, the count per circle of brick is 91 No. 1wedge'brick.

When used to form a circle as is commonly recommened for lining rotarykilns, such as the kiln described in the example given above, the brickcount is calculated so that theY brick have full face to face'contactwhen they re installed, that is, when the furnace is cold. At operatingtemperatures, however, one endlof the brick is 55 exposed to the furnacetemperature and the (Cl. 'I2-101) other end of the brick is subjected tothe cooling effects of radiation, and there is a temperaturedifferential between the ends of the brick. In rotary kiln servicetemperature differentials of 1500 F. to 2000" F. are not uncommon. It isobvious therefore that under such conditions the hot end of the brickmust have a greater percentage of total expansion than the cold end ofthe brick, and that the hot ends of the brick are subjected to terrificpressurescausing a continuous loss of a portion of the refractory.

The difference in "the percentage of total expansion in the hot end andthe cold end of a brick during periods of service changes the angularrelationship between the opposite faces of the brick, and thereforechanges the angular relationship between the opposite faces of thebrick, and therefore changes the angular relationship between thecontacting faces of adjacent brick. Consider, for example, the brick inan arched roof installed so as to have full face to face contact whencold. At furnace operating temperatures, the hot ends have a greaterpercentage of total expansion than the cold ends, the brick then haveonly approximately line to line contact at their hot ends and the hotends therefore must carry the total 'weight of the roof.

. The present invention has for its primary objects the elimination ofthe loss due to pinching off the hot ends of refractory units inservice.. and `of conditions which compel the hot ends lof the brick tocarry all the load, and contemplates for the attainment of these objects(1) the provision of a refractory structural unit which compensates forthe dierential expansion in refractories during service due totemperature differential between the ends of the brick, (2) a 'method offurnace construction in which the' above units are used and (3) afurnace structure composed of theabove refractory units.

These objects are attained by providing what will herein be calledpressure relief clearances between adjoining heat exposedv or inner endportions of the bricks. More specically, a spac-l ing material, forinstance refractory'` cement, is

interposed between the outer endportions of the brick, in such a mannerthat the inner end portions of any brick will have sufficient clearancewith adjoining brick, to allow for substantially free thermal expansionof the inner end portions of the brick under operating temperatureswithout undue encroachment of the brick upon one another.

' According to one feature a refractory structural unit or brickisc-upped, or has its one end u portion partly encased or surrounded byor coated with a layer of refractory cement, the thus conditioned brickconstituting a prefabricated-unit or article of manufacture.

According to another feature a refractory wall or lining is built up ofa combination of plain and partly coated brick in alternating order.

Still another feature has to do with a method of constructing refractorywalls or linings in a manner to allow for freedom of expansion of thepotentially hot end portion of lthe brick. More specifically, refractorycement which is interposed between or surrounds the outwardly locatedend portions of the brick, will weaken somewhat under the influence ofheat, thus causing pressure inequalities between the brick to compensatethemselves, yet without interfering with the desired freedom of thermalexpansion of the inner end portions of the brick.

The invention possesses other objects and features of advantage, some ofwhich, with the foregoing, will be set forth in the followingdescription. In the following description and in the claims, parts willbe identified by specific names for convenience, but they are intendedto be as generic in their application to similar parts as the art willpermit. In the accompanying drawings there has been illustrated the bestembodiment of the invention known to me, but such embodiment is to beregarded as typical only of many possible embodiments, and the invention,is not to be limited thereto.

The novel features considered characteristic of my invention are setforth with particularity in the appended claims. The invention itself,however, both as to its organization and its method of operation,together with additional objects and advantages thereof, will best beunderstood from the following description of a specific embodiment whenread in connection with the accompanying drawings in which:

Fig. 1 is a cross-section of a number of tapered brick disposed in archformation as inside the shell of a rotary kiln, indicating outlines(exaggerated) of the brick, assumed because of thermal expansion.

Fig. 2 is a section similar to that of Fig. 1, although through astraight wall.

Fig. 3 is a positive view indicating the assembly of a seriesofconditioned and plain brick in alternation.

Referring to the cross-section shown in Fig. 1, the numeral I designatesthe shell of a rotary kiln having a cylindrical lining of taperedbricks, a number of which are indicated by the numb-ers II, I2, I3 andI4. 'I'he dot and dash lines shown to surround the bricks, are toindicate the tendency of thermal expansion of the brick under serviceconditions. Brick I2 for example, dei-ined by the four corners, eachmarked a, when'cold would, under operating temperatures, expand in threedimensions, and the expanded cross-section of brick I2 would be definedby four new corners a1, a2, a3, a4, the inner or heat exposed endportion of the brick, of course, expanding at their greater rate thanthe outer colder or oifend of the brick, and the difference between theexpansion of the cold and the hot ends of the brick will herein becalled differential expansion. In other words, since the total expansionis the product of the temperature, the coefficient ofl expansion, andthe linear dimension, the hot ends of the brick, if free to move, willhave a greater percentage of total expansion than the cold ends, andbrick I2, for instance, would tend to assume outlines as defined by thecorner points a1, a2, a3, a4. The dimensions shown are illustrative onlyand have been exaggerated for the purpose of clarity. The pressurerelief clearances appearing between the brick when cold have beendesignated by the numeral I5.

As shown, the bricks have normally provided between them sufficientclearances I5 so that in their expanded state they will practically notmore than touch one another, whereas without such relief clearancesprovided according to the invention, the inner or hot end portions ofthe brick expanding at a relatively greater rate than the cooler outerend portions, would tend to encroach upon one another, and consequentlythe brick load would shift more and more on to the expanding hot endportions. Every brick in the circle'of the lining would thus be affectedin exactly the same fashion, and since it is impossible for the ring ofbricks to move to compensate for this tendency, the cumulative effect ofthe differential thermal expansion is a crushing effect which results inthe continuous pinching of the hot ends of the brick, thus reducing theservice rendered by the refractory lining.

In Fig. 1, in order to eliminate forcing the hot ends of the brick tocarry the load, and a'lso the pinching of the hot ends ofthe brick,each` brick, for example brick I2, has the end portion which is to berelatively cold in service, coated with a predetermined thickness of asolid refractory cement I6. That is to say, by combining therefractorybrick and cement in the manner according to this invention,or, as otherwise expressed, by a particular distribution of the cementor spacing material with respect to the refractory bricks, it ispossible to eliminate the pinching difficulties otherwise occurring inthe generally accepted method of refractory installation.

In one preferred embodiment the coating I6 covers from one-third toone-fourth of the length of the brick on the end which will not beexposed directly to the heat of the furnace, as distinguished from there facing end of the brick.

In constructing a furnace wall or lining with the aid of refractoryunits or bricks of this type, the hot ends 'of the expanded bricks willsubstantially merely touch upon kone another, while substantially thebulk of the load will still be carried by that portion of the brickwhich has been encased in cement. Moreover, the cement coating beingphysically weaker than the body of the brick to which it is applied,when subjected to compression will be forced to some extent into theclearances I5 between the hot edges of the brick. In this wayobjectionable pressure inequalities are being compensated, and thetendency to com'pel the hot ends of the brick to carry the load andpinch off the operating temperatures is virtually eliminated.

In Fig. 2 there is shown the embodiment of the invention as applied tothe construction of straight walls, the bricks used therein being theso-called "straights or squares This shows a section through a series ofbricks for example indicated by the numerals I1, I8, I9, 20, which asinstalled and in the cold state have the outlines defined by the pointsb at each corner of the cross-section, but which at operatingtemperatures, due to differential expansion between the hot ends and thecold ends of the brick move into positions b1, b2, b3, b4. The hot endsof the brick may touch one another at points f, the exhot ends, but alsoat 4the portions coated by the cement, and in fact the major portion ofthe weight of the wall is thus carried by the comparatively cold ends ofthe brick. With the materials and under conditions herein contemplatedfor use, as a matter of example, the cement coating being physicallyweaker than the body of the brick to which it is applied will let itselfbe compressed and forced into the clearances extending between it andthe hot edges of the brick. In

this way, the tendency to compel the hot ends of the brick to carry theload and to pinch off at operating temperatures, is virtuallyeliminated.

The method of constructing the refractory wall or lining by the use ofpartly coated or conditioned brick in alternation with plain brick, is

illustrated in Fig. 3 by showing in vertically superposed sequence acoated brick 23, a plain brick 24 above it, and again a coated brick 25on top of this. By breaking part of the coating away so from brick 25the character thereof is more clearly indicated.

Although the practice of this invention may not compensate exactly forall the changes in shape of refractory bricks or shapes duetotemperature differentials between the end exposed to the source ofheat and the other end, it does eliminate concentration of the load onthe hot end of the brick and prevents pinching off during service of thehot ends of the bricks or shapes due to differential expansion.

It is within the scope of my invention to provide furnace structures inwhich the partially coated shapes are used with regular uncoated shapesor with fully coated shapes in denite proportions, as for example astructure in which alternate bricks are provided with the partialcoating described herein, and the balance of the bricks are not socoated, (or completely coated) when the furnace temperatures and thecoeflicient of expansion of the refractory shape warrant suchconstruction.

I have described the partially coated bricks of my invention as havingbeen provided with a. dry

and rigid coating before delivery to the place of installation, but myinvention also contemplates the application of the coating by dipping,troweling, spraying or by any of the known methods at the place ofinstallation and immediately prior to installation, even permitting thedrying of the coating in place.

Although this invention is particularly applicable to chrome andmagnesite refractories, the principles also apply to all others. i

For example, on chrome brick I can use any of the better known chromecements, which may contain in addition to chrome ore such materials asclay, sodium silicate, periclase, nitre cake, water soluble sulphates,water soluble chlorides, starch or possibly others. On magnesite brick Ican use any of the better known magnesite or periclase cements, whichmay contain, in addition to magnesite or periclase, such materials assodium silicate, iron oxide, nitre cake, aluminum sulphate, watersoluble sulphates or chlorides, or possibly others.

I claim:

1. As an article of manufacture a refractory unit for use in furnacelinings which comprises a brick or shape having a portion thereofopposite the face to be exposed to the source of heat of the furnacecarrying a cementatory adhering coating, said coating being designed andadapted, after a number of said brick are assembled to form a wallsection of refractory lining, to act as spacing material between thebrick in a manner to discourage undesired pressure due to thermalexpansion, upon the undercut heat exposed end` portions of the brick,while in turn effective to transmit the load pressure directly frombrick to brick.

2. A unit according to claim 1, wherein the coating is rigid but weakerthan the brick or shape..

3. A unit according to claim l, wherein the coating surrounds a minorportion of the brick or shape.

4. A unit according to claim l, wherein the coating surrounds atleastall side faces of said coated end portion of the'brick.

5. A unit according to claim l, wherein the coating is of sufllcientthickness to discourage pinching-olfl of the uncoated ends of the bricksor shapes assembled in said furnace lining during periods of service.

' GILBERT E. SEIL.

